Post-transcriptional Mechanisms Research Articles

The splicing factor SF3B1 is essential for proper alternative splicing and zygotic genome activation in early porcine embryos

Alternative splicing (AS) is a pivotal posttranscriptional regulatory mechanism that is involved in embryonic development. However, the roles of AS in specific developmental events, especially the zygotic genome activation (ZGA) of porcine early embryos, remain unclear. In this study, we demonstrated that alternative splicing events (ASEs) were most prevalent in mammalian embryos during ZGA and that skipped exons were the predominant splicing pattern. When splicing factor 3B subunit 1 (SF3B1) was disrupted by the inhibitor pladienolide B (PlaB), we observed that porcine embryos were markedly arrested at the 4-cell stage. Concurrently, the main ZGA genes, namely, DPPA2, EIF6, and SORD, underwent aberrant splicing indicative of the failure of ZGA. Moreover, embryonic metabolic homeostasis was significantly disrupted at the 4-cell stage by SF3B1 inhibition, resulting in increases in the LDHA/LDHB ratio and lactate levels. Interestingly, the levels of the histone lactylation modifications pan-Kla and H4K5la also increased. Our findings enhance our understanding of early mammalian embryonic development, reveal the crucial role of porcine early embryogenesis, and help to resolve reproductive difficulties related to embryonic development.

Sex-specific mRNA alternative splicing patterns and Dmrt1 isoforms contribute to sex determination and differentiation of oyster.

Alternative splicing (AS) of pre-mRNA is a crucial mechanism that regulates the expression of genes involved in sex determination and differentiation. Despite its importance, AS has been rarely characterized in molluscs. In this study, PacBio Iso-Seq was employed to obtain full-length transcriptome and unveil AS patterns of gonads in the Pacific oyster Crassostrea gigas. A total of 24,783 AS events were identified across 6259 genes, with many enriched in phosphorylation-related processes. Splicing factors were found to drive a high frequency of AS events in gonads. Significant sex-based differences in isoform abundance and the incidence of AS events were observed. Comparative analysis of mature female and male gonads revealed a subset of overlapping differential alternative splicing genes and differentially expressed genes enriched in processes related to microtubule function and cell motility. In addition, the expression levels of sex-biased genes were found correlated with their isoform number in both female and male gonads. A novel isoform of Dmrt1 was identified with male specific expression in mature gonads. This study provides the first comprehensive understanding of full-length transcriptome and AS patterns in molluscan gonads, shedding light on the post-transcriptional regulatory mechanisms underlying sex determination and differentiation in molluscs and potentially across other animals.

Wheat Tae-MIR1118 Constitutes a Functional Module With Calmodulin TaCaM2-1 and MYB Member TaMYB44 to Modulate Plant Low-N Stress Response.

Distinct target genes are modulated by microRNA members and affect various biological processes associated with abiotic stress responses in plants. In this study, we characterized a functional module comprising miRNA/target and a downstream MYB transcription factor partner, Tae-MIR1118/TaCaM2/TaMYB44, in Triticum aestivum to mediate the plant low-nitrogen (N) stress response. Dual luciferase (LUC) assay and expression analysis indicated that TaCaM2 is regulated by Tae-MIR1118 through a posttranscriptional cleavage mechanism. Reporter LUC activity in N. benthamiana leaves co-transformed with effector CaMV35S::Tae-MIR1118 and reporter TaCaM2::LUC was significantly reduced, and the transcripts of Tae-MIR1118 and TaCaM2 in tissues exhibited converse expression patterns under varying N levels. Specifically, the transcripts of Tae-MIR1118 decreased, whereas those of TaCaM2 increased under low-N stress in a temporal-dependent manner. Yeast two-hybrid, bimolecular fluorescence complementation (BiFC) and co-immunoprecipitation (Co-IP) assays indicated that TaCaM2 interacted with the MYB transcription factor TaMYB44. Transgene analysis revealed the negative roles of Tae-MIR1118 and the positive functions of TaCaM2 and TaMYB44 in regulating plants for low-N stress adaptation by modulating glutamine synthetase activity, N uptake capacity, and root morphology. Yeast one-hybrid, transcriptional activation, and chromatin immunoprecipitation-quantitative polymerase chain reaction (ChIP-PCR) assays indicated that TaMYB44 could bind to the promoters of genes TaGS2.2, TaNRT2.1, and TaPIN4 and induce transcription of these stress-defensive genes. Knockdown of these three genes reduced GS activity, N accumulation, and root growth traits in plants subjected to N starvation. The yield in the wheat variety panel was highly correlated with the transcripts of Tae-MIR1118, TaCaM2, and TaMYB44 in plants cultured under N-deprived field conditions. A major haplotype of Tae-MIR1118, TaMIR1118-Hap1, enhanced the low-N stress tolerance of plants. Our findings indicate that the Tae-MIR1118/TaCaM2/TaMYB44 pathway primarily affects the low-N response of plants by modulating associated physiological processes.

Soluble αβ-tubulins reversibly sequester TTC5 to regulate tubulin mRNA decay

Microtubules, built from heterodimers of α- and β-tubulins, control cell shape, mediate intracellular transport, and power cell division. The concentration of αβ-tubulins is tightly controlled through a posttranscriptional mechanism involving selective and regulated degradation of tubulin-encoding mRNAs. Degradation is initiated by TTC5, which recognizes tubulin-synthesizing ribosomes and recruits downstream effectors to trigger mRNA deadenylation. Here, we investigate how cells regulate TTC5 activity. Biochemical and structural proteomic approaches reveal that under normal conditions, soluble αβ-tubulins bind to and sequester TTC5, preventing it from engaging nascent tubulins at translating ribosomes. We identify the flexible C-terminal tail of TTC5 as a molecular switch, toggling between soluble αβ-tubulin-bound and nascent tubulin-bound states. Loss of sequestration by soluble αβ-tubulins constitutively activates TTC5, leading to diminished tubulin mRNA levels and compromised microtubule-dependent chromosome segregation during cell division. Our findings provide a paradigm for how cells regulate the activity of a specificity factor to adapt posttranscriptional regulation of gene expression to cellular needs.

Altered expression of Csnk1a1p in Autism Spectrum Disorder in Iranian population: case-control study

Over the past decade, substantial scientific evidence has showed that long non-coding RNAs (lncRNAs) are extensively expressed and play a crucial role in gene modulation through a diverse range of transcriptional, and post-transcriptional mechanisms. Recent discoveries have emphasized the involvement of lncRNAs in maintaining cellular homeostasis and neurogenesis in the brain. Accumulating reports identified dysregulated lncRNAs associated with psychiatric disorders, including autism. In this study, we examined the expression levels of DISC2, Linc00945, Foxg1-as1, Csnk1a1p, and Evf2 lncRNAs in blood samples from 21 clinically diagnosed autistic patients based on the Diagnostic and Statistical Manual of Mental Disorders criteria-5th edition (DSM-5), compared to age, sex, and ethnically-matched 25 healthy individuals. RNA extraction and cDNA synthesis were performed, followed by real-time PCR for quantification of lncRNAs expression levels. Receiver operating characteristic (ROC) curve analysis was used to evaluate biomarker potential. Additionally, we investigated the correlation between gene expression levels and autism comorbidities. Our results showed a significant decrease in Csnk1a1p expression in patients with autism spectrum disorder (ASD) compared to healthy children (P value = 0.0008). ROC curve analysis indicated that Csnk1a1p expression levels could effectively discriminate patients from healthy controls (AUC = 0.837, P value = 0.000284). No significant differences were observed between Csnk1a1p expression levels and comorbidity with ADHD or intellectual disability (p-value > 0.05). Based on these findings, Csnk1a1p may play a significant role in autistic patients and could serve as a potential biomarker for diagnostic and predictive purposes, as well as a therapeutic target.

Abstract A001: HNRNPH1 regulates the alternative splicing of transcripts expressed by cancer-associated genes

Abstract The RNA binding protein HNRNPH1 is a critical regulator of alternative splicing (AS). We have previously demonstrated that HNRNPH1 mediates an exon exclusion event required for the expression of the mRNA encoding the fusion oncoprotein expressed in a subset (∼37%) of Ewing sarcomas. Furthermore, studies by others have shown that HNRNPH1 regulates a mutually exclusive exon (MXE) AS event (exon-18a versus exon-18b) that defines the expression of TCF3 transcript variants, which, when dysregulated, promotes tumorigenesis in Burkitt’s lymphoma. In this study, we have interrogated the transcriptome-wide effects of depleting HNRNPH1 by RNAi to further explore its regulation of transcripts expressed by cancer-associated genes. We performed whole transcriptome RNA sequencing (RNAseq; short-read, Illumina; long-read, PacBio IsoSeq) of two cell lines (HEK-293T and HT-1080) post 48-hour transfection with a control siRNA (siNeg) or an siRNA targeting HNRNPH1 (siHNRNPH1). We then assembled a workflow to quantify changes in individual AS events (percent-spliced-in, ΔPSI=±0.1) using rMATS and MAJIQ, and differential transcript expression (DTE) using RSEM (pValue≤0.05) and EBSeq (FDR≤0.05). RNAseq analyses were validated using PCR assays. The rMATS analysis revealed skipped exons (SE) as the most frequent event effected in HEK-293T and HT-1080 cells following HNRNPH1 silencing, with 1069 SE or MXE events from 607 genes common to both. Gene annotation (Metascape) of these 607 genes identified 49 as cancer-associated. Consistent with previous studies, we detected a significant change in the TCF3-exon-18a/18b MXE event using rMATS (decreased PSI for 18a) and MAJIQ (negative ΔPSI for 18a and positive ΔPSI for 18b) following HNRNPH1 silencing in both cell lines. Furthermore, DTE revealed a corresponding decrease in 18a-containing TCF3-transcripts and an increase in 18b-containing TCF3-transcripts, validating our analytical pipeline. Next, we extended our analysis to uncharacterized HNRNPH1-regulated AS events, beginning with examination of transcripts encoding the mitotic kinase AURKA. Previous studies have shown that AS of AURKA transcripts localizes to the untranslated regions (UTRs), particularly the 5’UTR. However, regulators of these AS events are unknown, and it is unclear how these UTR variants affect AURKA protein expression. Long-read RNAseq of AURKA mRNAs from both cell lines revealed extensive 5’UTR AS, and the rMATS and MAJIQ analyses showed decreased PSI and negative ΔPSI for a specific 5’UTR-exon following HNRNPH1 silencing. DTE revealed corresponding decreases in abundance of AURKA transcripts containing this exon (AURKA-203, -205, -209, and -213) upon HNRNPH1 depletion, which we confirmed with variant-specific RT-PCR. Furthermore, immunoblot analysis showed a decrease in AURKA protein expression following the silencing of HNRNPH1. Our assessment of AURKA AS suggests HNRNPH1 mediates the inclusion of a specific AURKA-5’UTR-exon, providing evidence for a previously uncharacterized post-transcriptional regulatory mechanism of AURKA expression. Citation Format: Tayvia Brownmiller, Patricio Pichling, Tamara L Jones, Ioannis Grammatikakis, Soumya Sundara Rajan, Erica C Pehrsson. HNRNPH1 regulates the alternative splicing of transcripts expressed by cancer-associated genes [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: RNAs as Drivers, Targets, and Therapeutics in Cancer; 2024 Nov 14-17; Bellevue, Washington. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(11_Suppl):Abstract nr A001.

Snapshot Moments of the Cell Revealed by UV-Crosslinking and RNA Co-immunoprecipitation of Transient RNA-Protein Complexes.

RNA co-immunoprecipitation serves as a powerful technique for elucidating the interactions between RNA and RNA-binding proteins, pivotal for understanding posttranscriptional regulation mechanisms. This method captures the dynamics of protein-RNA associations across various cellular processes, applicable to both coding and noncoding RNAs. Here we describe a convenient and compelling method using nanobody coupled beads and UV-crosslinking. Importantly, this method can also be utilized to isolate short-lived complexes, for instance in RNA-degradation. The obtained RNA can be used for many downstream applications, such as qPCR or RNA-sequencing.

Reduced expression of FOXE1 in differentiated thyroid cancer, the contribution of CPG methylation, and their clinical relevance.

Forkhead box E1 (FOXE1) is a transcription factor with a crucial role in thyroid morphogenesis and differentiation. Promoter hypermethylation downregulates FOXE1 expression in different tumor types; nevertheless, its expression and relationship with methylation status in differentiated thyroid cancer (DTC) remain unclear. A total of 33 pairs of matched samples of PTC tumors and non-tumors were included. Tumor cell cultures were treated with either 5-Aza-2'-deoxycytidine demethylating agent or dimethyl sulfoxide (DMSO). A real-time polymerase chain reaction (RT-PCR) and Western blotting were performed to assess FOXE1 expression. The methylation status was quantified using bisulfite sequencing. A luciferase gene assay was used to determine CpG-island functionality. Gene expression and promoter methylation of FOXE1 and FOXE1-regulated genes were also analyzed with data from The Cancer Genome Atlas (TCGA) thyroid samples. After demethylating treatment, increased FOXE1 mRNA was observed concomitantly with reduced promoter methylation of CpGisland2. A negative correlation between mRNA downregulation and an increased methylation level of CpGisland2 was observed in tumors. Diminished protein expression was also detected in some DTC cell lines and in some tumor samples, suggesting the involvement of post-transcriptional regulatory mechanisms. CPGisland2 was proved to be an enhancer. TCGA data analysis showed low FOXE1 mRNA expression in tumors with a negative correlation with methylation status and a positive correlation with the expression of most of its target genes. Reduced FOXE1 expression, accompanied by a high methylation level, was associated with PTC aggressiveness (tall cell variant, advanced extra thyroid extension, T4 American Joint Committee on Cancer (AJCC) classification), age at diagnosis (over 45 years old), and presence of a BRAFV600E mutation. FOXE1 mRNA was downregulated in DTC compared with non-tumors, followed by high CpGisland methylation. A coupling of low mRNA expression and high methylation status was related to characteristics of aggressiveness in DTC tumors.

TOR Inhibition Enhances Autophagic Flux and Immune Response in Tomato Plants Against PSTVd Infection.

Viroids are small, non-coding RNA pathogens known for their ability to cause severe plant diseases. Despite their simple structure, viroids like Potato Spindle Tuber Viroid (PSTVd) can interfere with plant cellular processes, including transcriptional and post-transcriptional mechanisms, impacting plant growth and yield. In this study, we have investigated the role of the Target Of Rapamycin (TOR) signaling pathway in modulating viroid pathogenesis in tomato plants infected with PSTVd. Our findings reveal that PSTVd infection induces the accumulation of the selective autophagy receptor NBR1, potentially inhibiting autophagic flux. Pharmacological inhibition of TOR with AZD8055 mitigated PSTVd symptomatology by reducing viroid accumulation. Furthermore, TOR inhibition promoted the recovery of autophagic flux through NBR1. It primed the plant defense response, as evidenced by enhanced expression of the defense-related gene PR1b and S5H, a gene involved in the salicylic acid catabolism. These results suggest a novel role for TOR in regulating viroid-induced pathogenesis and highlight the potential of TOR inhibitors as tools for enhancing plant resistance against viroid infections.

PKC-mediated phosphorylation governs the stability and function of CELF1 as a driver of EMT in breast epithelial cells

Epithelial to mesenchymal transition (EMT) is believed to be a principal factor contributing to cancer metastasis. The post-transcriptional and post-translational mechanisms underlying EMT are comparatively underexplored. We previously demonstrated that the CELF1 RNA binding protein is necessary and sufficient to drive the EMT of breast epithelial cells, and that the relative protein expression of CELF1 in this context was dictated at the post-translational level. Here, we elucidate the mechanism of this regulation. Mass spectrometric analysis of CELF1 isolated from mesenchymal MCF-10A cells identified multiple sites of serine and threonine phosphorylation on the protein, correlating with the increased stability of this protein in this cellular state. Analysis of phosphomimetic and serine/threonine-to-alanine phosphomutant variants of CELF1 revealed that these phosphorylation sites indeed dictate CELF1 stability, ubiquitination state, and function in vitro. Via co-immunoprecipitation and in vitro kinase assays, we identified the Protein Kinase C (PKC) alpha and epsilon isozymes as the kinases responsible for CELF1 phosphorylation in a breast cell line. Genetic epistasis experiments confirmed that these PKCs function upstream of CELF1 in this EMT program, and CELF1 phosphorylation impacts tumor metastasis in a xenograft model. This work is the first to formally establish the mechanisms underlying post-translational control of CELF1 expression and function during EMT of breast epithelial cells. Given the broad dysregulation of CELF1 expression in human breast cancer, our results may ultimately provide knowledge that may be leveraged for novel therapeutic interventions in this context.

Evaluation of Interfering RNA Efficacy in Treating Hepatitis B: Is It Promising?

Despite an existing safe and effective vaccine for hepatitis B virus (HBV), it is still a major public health concern. Nowadays, several drugs are used to treat chronic hepatitis B; however, full healing remains controversial. The viral covalently closed circular DNA (cccDNA) formed by HBV forms a major challenge in its treatment, as does the ability of HBV to integrate itself into the host genome, which enables infection reactivation. Interfering RNA (RNAi) is a gene-silencing post-transcriptional mechanism which forms as a promising alternative to treat chronic hepatitis B. The aim of the present review is to assess the evolution of hepatitis B treatment approaches based on using RNA interference. Data published between 2016 and 2023 in scientific databases (PubMed, PMC, LILACS, and Bireme) were assessed. In total, 76,949 articles were initially identified and quality-checked, and 226 eligible reports were analyzed in depth. The main genomic targets, delivery systems, and major HBV therapy innovations are discussed in this review. This review reinforces the therapeutic potential of RNAi and identifies the need for conducting further studies to fill the remaining gaps between bench and clinical practice.

The role of m5C RNA methylation regulators in the diagnosis and immune microenvironment of osteoarthritis

The 5-methylcytosine (m5C) is a common post-transcriptional RNA methylation modification and is involved in the pathological process of many diseases. However, little is known about the role of m5C in osteoarthritis (OA). OA gene data and the corresponding information were downloaded from the Gene Expression Omnibus database. Based on 36 m5C regulators, we constructed the landscape and diagnostic model for OA. Later, two m5C modification patterns were identified, and functional analyses were performed to evaluate whether these patterns were related to endoplasmic reticulum (ER) stress and mitochondrial autophagy. We further comprehensively analyzed the immune cell infiltration characteristics in different modification patterns in OA. We also established the post-transcriptional regulatory networks and drug-gene networks. Our findings suggested that m5C regulators were differentially expressed between OA and normal samples and could serve as novel biomarkers for the diagnosis of OA. Besides, m5C regulators may be involved in regulating ER stress, mitochondrial autophagy, and immune infiltration in OA. The m5C modification can influence the sensitivity to drugs and the potential post-transcriptional regulatory mechanisms might provide promising targets.

RPS 2.0: an updated database of RNAs involved in liquid-liquid phase separation.

Liquid-liquid phase separation (LLPS) is a crucial process for the formation of biomolecular condensates such as coacervate droplets, P-bodies and stress granules, which play critical roles in many physiological and pathological processes. Increasing studies have shown that not only proteins but also RNAs play a critical role in LLPS. To host LLPS-associated RNAs, we previously developed a database named 'RPS' in 2021. In this study, we present an updated version RPS 2.0 (https://rps.renlab.cn/) to incorporate the newly generated data and to host new LLPS-associated RNAs driven by post-transcriptional regulatory mechanisms. Currently, RPS 2.0 hosts 171 301 entries of LLPS-associated RNAs in 24 different biomolecular condensates with four evidence types, including 'Reviewed', 'High-throughput (LLPS enrichment)', 'High-throughput (LLPS perturbation)' and 'Predicted', and five event types, including 'Expression', 'APA', 'AS', 'A-to-I' and 'Modification'. Additionally, extensive annotations of LLPS-associated RNAs are provided in RPS 2.0, including RNA sequence and structure features, RNA-protein/RNA-RNA interactions, RNA modifications, as well as diseases related annotations. We expect that RPS 2.0 will further promote research of LLPS-associated RNAs and deepen our understanding of the biological functions and regulatory mechanisms of LLPS.

Analysis of Alternative Splicing Events and Identification of Key Genes in Brassica napus Leaves Infected by Leptosphaeria biglobosa

Alternative splicing (AS) is a prevalent post-transcriptional regulatory mechanism in eukaryotes and plays a crucial role in plant disease resistance. Here, we used the Illumina Novaseq sequencing platform to conduct transcriptome sequencing on canola (Brassica napus) leaves infected with the blackleg pathogen (Leptosphaeria biglobosa strain nm−1) at 0 h, 72 h, 120 h, and 168 h post-inoculation to investigate the mechanism of AS coordination with transcriptional regulation in canola’s response to blackleg disease. The rMATS software (4.1.0) was employed to analyze different AS events in samples taken at 72 h, 120 h, and 168 h. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed to elucidate the biological functions of differentially spliced genes at various time points, while Weighted Gene Co-expression Network Analysis (WGCNA) was used to identify key modules and hub genes. As a result, our analysis reveals 16908 AS events across three time points, with 221 being differently spliced. Intron retention (RI) was the most common AS event, accounting for approximately 55% of all events, while alternative 5′ splice site events were least common, comprising only 2%. Furthermore, a total of 213 significantly differentially spliced genes were identified, which were enriched in functions related to protein kinase activity, transferase activity, and pathways such as MAPK signaling pathway—plant and plant hormone signal transduction. WGCNA identified three key modules and ten hub genes, including calcium-binding transcription activator 1, LRR class receptor serine/threonine protein kinase FEI 2, PLATZ transcription factor family proteins, serine/threonine protein kinase PRP4, and E3 ubiquitin ligase SUD1, all of which are associated with canola resistance to L. biglobosa. Thus, this study provides a theoretical basis for identifying disease-resistance genes involved in AS and for exploring the functions of AS gene isoforms in canola.

Identification of exosomal ceRNA networks as prognostic markers in clear cell renal cell carcinoma.

Aggressive clear cell renal cell carcinoma (ccRCC) has a bad prognosis. We seek new ccRCC biomarkers for diagnosis and treatment. We used exoRBase and The Cancer Genome Atlas Database to compare DEmRNAs, DEmiRNAs, DElncRNAs, and DEcircRNAs in ccRCC and normal renal tissues. CircRNAs and circRNAs targeting microRNAs (miRNAs) were anticipated and taken intersections, and several databases assessed the targeted link between common miRNAs and messenger RNAs (mRNAs). The Cancer Genome Atlas database was used to create a predictive mRNA signature that was validated in E-MTAB-1980. Finally, we examined competing endogenous RNA network miRNAs and long noncoding RNAs for ccRCC predictive biomarkers using overall survival analysis. We built the first competing endogenous RNA regulation network of circRNA-lncRNA-miRNA-mRNA and found that it substantially correlates with ccRCC prognosis. We unveiled ccRCC's posttranscriptional regulation mechanism in greater detail. Our findings identified novel biomarkers for ccRCC diagnosis, therapy, and prognosis.

Neuron-selective and activity-dependent splicing of BDNF exon I–IX pre-mRNA

Brain-derived neurotrophic factor (BDNF) is essential for numerous neuronal functions, including learning and memory. The expression of BDNF is regulated by distinctive transcriptional and post-transcriptional mechanisms. The Bdnf gene in mice and rats comprises eight untranslated exons (exons I–VIII) and one exon (exon IX) that contains the pre-proBDNF coding sequence. Multiple splice donor sites on the untranslated exons and a single acceptor site upstream of the coding sequence result in the characteristic exon skipping patterns that generate multiple Bdnf mRNA variants, which are essential for the spatiotemporal regulation of BDNF expression, mRNA localization, mRNA stability, and translational control. However, the regulation of Bdnf pre-mRNA splicing remains unclear. Here, we focused on the splicing of Bdnf exon I–IX pre-mRNA. We first constructed a minigene to evaluate Bdnf exon I–IX pre-mRNA splicing. Compared with Bdnf exon I–IX pre-mRNA splicing in non-neuronal NIH3T3 cells, splicing was preferentially observed in primary cultures of cortical neurons. Additionally, a series of overexpression and knockdown experiments suggested that neuro-oncological ventral antigen (NOVA) 2 is involved in the neuron-selective splicing of Bdnf exon I–IX pre-mRNA. Supporting this finding, endogenous Nova2 mRNA expression was markedly higher in neurons, and a strong correlation between endogenous Bdnf exon I–IX and Nova2 mRNA was observed across several brain regions. Furthermore, Bdnf exon I–IX pre-mRNA splicing was facilitated by Ca2+ signals evoked via L-type voltage-dependent Ca2+ channels. Notably, among the Bdnf pre-mRNA splicing investigated in the current study, neuron-selective and activity-dependent splicing was observed in Bdnf exon I–IX pre-mRNA. In conclusion, Bdnf exon I-IX pre-mRNA splicing is preferentially observed in neurons and is facilitated in an activity-dependent manner. The neuron-selective and activity-dependent splicing of Bdnf exon I–IX pre-mRNA may contribute to the efficient induction of Bdnf exon I–IX expression in neurons.

Identification and Validation of the Hsa_circ_0001726/miR-140-3p/KRAS Axis in Hepatocellular Carcinoma Based on Microarray Analyses and Experiments.

Hepatocellular carcinoma (HCC) is one of the most fatal malignancies. Epigenetic mechanisms have revealed that noncoding RNAs, such as microRNAs (miRNAs) and circular RNAs (circRNAs), are involved in HCC progression. This study aimed to construct a circRNA-miRNA-mRNA network in HCC and validate one axis within the network. HCC-related transcriptome data were obtained from the Gene Expression Omnibus, and HCC-related genes were sourced from GeneCards to identify differentially expressed circRNAs and miRNAs. The targeting relationships between circRNA-miRNA and miRNA-mRNA interactions were predicted. The involvement of the hsa_circ_0001726/miR-140-3p/KRAS axis in HCC was evaluated through cellular experiments and survival analyses. We identified six differentially expressed circRNAs in HCC, which were linked to 13 miRNAs and 88 mRNAs. A network containing 34 circRNA-miRNA pairs and 194 miRNA-mRNA pairs was constructed. Cell proliferation and migration assays confirmed the role of hsa_circ_0001726 in promoting HCC progression, possibly through the miR-140-3p/KRAS axis. Survival analysis verified that hsa_circ_0001726 was a prognostic factor for overall survival in patients with HCC. The hsa_circ_0001726/miR-140-3p/KRAS axis also mediates lenvatinib resistance in HCC cells. The HCC circRNA/miRNA/mRNA network provides new insights into the post-transcriptional regulatory mechanism of HCC. The hsa_circ_0001726/miR-140-3p/KRAS axis is involved in HCC progression and lenvatinib resistance.

Disrupted Post-Transcriptional Regulation of Gene Expression as a Hallmark of Fatty Liver Progression

It is known that both transcriptional and post-transcriptional mechanisms control messenger RNA (mRNA) levels. Compared to transcriptional regulations, our understanding of how post-transcriptional regulations adapt during fatty liver progression at the whole-transcriptome level is unclear. While traditional RNA-seq analysis uses only reads mapped to exons to determine gene expression, recent studies support the idea that intron-mapped reads can be reliably used to estimate gene transcription. In this study, we analyzed differential gene expression at both the exon and intron levels using two liver RNA-seq datasets from mice that were fed a high-fat diet for seven weeks (mild fatty liver) or thirty weeks (severe fatty liver). We found that the correlation between gene transcription and mature mRNA levels was much lower in mice with mild fatty liver as compared with mice with severe fatty liver. This result indicates broad post-transcriptional regulations for early fatty liver and such regulations are compromised for severe fatty liver. Specifically, gene ontology analysis revealed that genes involved in synapse organization and cell adhesion were transcriptionally upregulated, while their mature mRNAs were unaffected in mild fatty liver. Further characterization of post-transcriptionally suppressed genes in early fatty liver revealed that their mRNAs harbor a significantly longer 3′ UTR, one of the major features that may subject RNA transcripts to nonsense-mediated RNA decay (NMD). We further show that the expression of representative genes that were post-transcriptionally suppressed were upregulated in mice with a hepatocyte-specific defect of NMD. Finally, we provide data supporting a time-dependent decrease in NMD activity in the liver of a diet-induced metabolic-dysfunction-associated fatty liver disease mouse model. In summary, our study supports the conclusion that NMD is essential in preventing unwanted/harmful gene expression at the early stage of fatty liver and such a mechanism is lost due to decreased NMD activity in mice with severe fatty liver.

MicroRNA miR-210 Modulates the Water Flea Daphnia magna Response to Cyanobacterial Toxicity.

As a key form of post-transcriptional regulation, microRNAs (miRNAs) regulate gene expression by binding to target mRNAs, leading to mRNA decay or translational repression. Recently, the role of miRNAs in the response of aquatic organisms to environmental stressors has emerged. Daphnia, widely distributed cladocerans, play a crucial role in aquatic ecosystems. Cyanobacterial blooms often cause Daphnia populations to decrease, thereby disrupting ecosystem functionality and water quality. However, the post-transcriptional mechanisms behind Daphnia's response to toxic cyanobacteria are insufficiently understood. This study investigated the role of miR-210, a multifunctional miRNA involved in stress response and toxicity pathways, and its target genes (MLH3, CDHR5, and HYOU1) in two Daphnia magna clones exposed to toxic Microcystis aeruginosa. Results showed that M. aeruginosa inhibited somatic growth rates, led to microcystin accumulation, caused abnormal ultrastructural alterations in the digestive tract, and induced DNA damage in both clones. Notably, exposure significantly increased miR-210 expression and decreased the expression of its target genes compared with the controls. We identified miR-210s regulation on clonal-tolerance variations in D. magna to M. aeruginosa, emphasizing miRNAs' contribution to adaptive responses. Our work uncovered a novel post-transcriptional mechanism of cyanobacterial impact on zooplankton and provided essential insights for assessing cyanobacterial toxicity risks.

A Genome-Wide Alternative Splicing Analysis of Gossypium arboreum and Gossypium raimondii During Fiber Development

Alternative splicing (AS) is a crucial post-transcriptional regulatory mechanism that contributes to proteome complexity and versatility in different plant species. However, detailed AS exploration in diploid cotton during fiber development has not been reported. In this study, we comparatively analyzed G. arboreum and G. raimondii AS events during fiber development using transcriptome data and identified 9690 and 7617 AS events that were distributed in 6483 and 4859 genes, respectively. G. arboreum had more AS genes and AS events than G. raimondii, and most AS genes were distributed at both ends of all 13 chromosomes in both diploid cotton species. Four major AS types, including IR, SE, A3SS, and A5SS, were all experimentally validated through RT-PCR assays. G. arboreum and G. raimondii had only 1888 AS genes in common, accounting for one-third and one-half of the total number of AS genes, respectively. Furthermore, we found a lysine-specific demethylase coding gene with a different AS mechanism in G. arboreum and G. raimondii, in which AS isoforms lacked part of a key conserved domain. Our findings may provide new directions for the discovery of functional genes involved in cotton species differentiation.